1. Field of the Invention
This invention relates to trimmers, such as those used to sever vegetation and, more particularly, to a trimmer having separate cutting blades with cutting edges that cooperate as relative movement between the cutting blades is effected.
2. Background Art
A well known trimmer construction consists of cooperating cutting blades that are moved, one guidingly against the other, to cause cutting edges on the cutting blades to interact to effect severance of material, such as vegetation. Myriad different designs for these trimmers are currently in existence. In one exemplary form, the separate cutting blades are elongate and have cooperating surfaces that move guidingly, one against the other, to produce a cutting action as the cutting edges thereon are caused to repetitively interact with a scissors-type action. Ideally, the cutting blade surfaces move, one against the other, without excessive binding. Exemplary mechanisms for accomplishing this, and some associated drawbacks, will now be described.
In one design, the cutting blades are operatively connected to a support bar on a frame associated with a drive mechanism, that could be an internal combustion engine, or an electrically operated motor. A number of bolts are directed through the cutting blades and are threadably connected to the support bar so that the blades become captive between the support bar and the heads of the bolts. The bolts are tightened and thereafter backed off ¼ to ½ turn to allow sufficient clearance between the blades that they can be guided, one against the other, without significant resistance.
This mechanism has an advantage that it allows the spacing between the blades to be changed after there has been wear thereon that increases the clearance to beyond what is optimal. As the clearance increases beyond a certain amount, the cutting effectiveness may diminish. The blades may at some point be prone to jamming as when material wedges between the cooperating surfaces.
The drawback with this system is that the adjustment may be made by the end user in the field. Some users may find the adjustment process difficult or confusing, whereas others may not wish to take the time necessary to adjust the bolts.
In an alternative design, a rigid spacer may be fixed between a support bar and the bottom cutting blade. A bolt is tightened until the relationship between the support bar and bottom blade is fixed. This space is not adjustable and therefor is fixed as dictated by the configuration of the spacer.
Over time, as noted above, the repetitive rubbing action of the blades, one against the other, may cause wear that increases the spacing between the cooperating cutting blade surfaces. Eventually, the clearance between the blade surfaces may be such that the blades are detrimentally movable away from each other to the point that the cutting blades will not effectively sever the material for which they are designed or become jammed by material that is being cut.
The industry continues to seek improved designs of this type of mechanism wherein the cooperating cutting blade surfaces may be consistently maintained in relationship to each other and a support bar so that optimal cutting occurs, even after there has been normal anticipated wear of the cutting blades after extended use.